According to Tim Henman, a few rain showers could help Roger Federer notch up a record-equalling seventh appearance on the honours board.

This theory revolves around the fact that Federer stands unchallenged as the master of indoor courts, as he proved last winter by romping to back-to-back titles in Paris and London.

“If the Centre Court roof comes over,” Henman says, “you will be talking about the world’s first indoor grand slam.”

As a long-time friend and admirer of Federer, Henman finds it bewildering that so many pundits and commentators are prepared to write off the greatest winning machine the game has seen. Particularly at Wimbledon, where Federer’s tally of six championships leaves him one short of Pete Sampras’s magnificent seven.

“If he wins another grand slam – and I believe he will – then I would expect him to do it at Wimbledon or the US Open,” Henman said.

“The surface in New York is actually faster, but the nature of the movement on a grass court means it is a difficult place to defend. Federer doesn’t really do much defending because his style is so aggressive.

“We saw him lose to Novak Djokovic in Paris in very unhelpful, windy conditions, which suited Djokovic’s attritional approach. You have to play with a far greater margin for error when it’s windy.

"You can’t aim as close to the lines. Certainly on a clay court with a slightly irregular bounce you can’t take the ball so early.

“But I’d like to see Roger play Novak under the Wimbledon roof. I think that might produce a different result, because right now, he is the best indoor player in the world.”

Henman has always had a strong relationship with Federer, stretching back to the year when they met in the quarter-finals of Wimbledon in 2001.

Henman won that match in four sets, and at one point in 2004 he had a record of six wins from seven head-to-head encounters (though Federer would eventually reclaim the lead in the series).

Even since Henman’s retirement in 2007, their bond has endured. And it has also proved profitable for Paul Annacone, the American coach who has worked with both of them. It was Henman’s recommendation to Federer that earned Annacone one of the most sought-after jobs in tennis.

Henman still keeps in touch with his old friends and assured Telegraph Sport that Federer has never been in better shape to add to his vast collection of silverware.

“I would bet that 99 per cent of the players want to be playing at Roger’s level right now,” he said. “So why are so many people writing him off?

“The challenge for Roger right now is obviously Djokovic and Rafael Nadal, two of the greatest players of all time, but what a great challenge to have. I actually think that Roger’s best level now is higher than it was when he was winning everything in sight; it’s just that everyone else has improved too.

“Let’s go back to last year’s US Open. He had match point against Djokovic, and Djokovic hit a one-in-a-hundred shot. If you move forward from that, in the last nine months he has won seven tournaments. He’s 30 years old, but he’s in phenomenal shape. His hunger and desire are as great as anyone’s.

Andre Agassi made the final of the US Open at 35, and he was nothing like as natural an athlete as Roger.

“We’re very good in focusing — certainly in this country — on what we haven’t got. With someone like Federer, goodness, let’s try and keep him around for as long as possible. He’s the best player that’s ever lived, so let’s enjoy him while he’s here.”

The question of how long Federer will go on for has diverted plenty of tennis insiders, but the truth is that no one really knows. Possibly not even Federer himself.

At some point, he will presumably find that diminishing returns kick in. But for a man who stands well clear of Andy Murray at No 3 in the world, that day must still be some way off.

“I think Roger appreciates how lucky it is and the opportunity he’s got,” Henman said, “and he wants to make the most of it. I stopped at exactly the right time.

"I was 33 and was struggling with different aspects, especially as we had just had our third child. But the reality is that there’s plenty of time to be retired.

While you’re an athlete playing at the highest level you want to make the most of it.” And we who follow the game should make the most of Federer too. To paraphrase George Orwell, all players are unique, but some are more unique than others.

Tim Henman is an ambassador for HSBC, Official Banking Partner to the Wimbledon Championships, www.wimbledon.com/hsbc